I have a patient who has changed insurance companies during her pregnancy. She became a new OB patient on 10/25/07 and has had 9 visits during her coverage under 'Plan A'. Effective 4/1/08 she will be covered under 'Plan B.' Her expected date of delivery is May 3,2008. At this point, I am assuming she will be seen for at least 4 visits under 'Plan B.' I am not sure how to bill the visits to 'Plan A' for her 9 antepartum visits. Should I bill CPT 59426 to 'Plan A' and the delivery code 59400-52 to 'Plan B'? (I am appending modifier -52 to 'Plan B' insurance since she will be seen for less than 13 antepartum visits). Naturally, these claims will not be filed until after her delivery. Please advise and thanks in advance!